1. Field of the Invention
This invention relates to a hydraulic adjustable vibration damper with a piston fastened to a piston rod and dividing a work cylinder into two work chambers filled with damping fluid, whereby at least partly to control the damping force, an electromagnetically activated damping valve consisting of a coil, a magnetic armature, a valve body and a valve seat pressurizes a flow passage.
2. Background Information
There may be known hydraulic adjustable vibration dampers (e.g. U.S. Pat. No. 4,850,460, entitled Hydraulic Adjustable Shock Absorber, which corresponds to Federal Republic of Germany Patent No. 37 12 477; and U.S. Pat. No. 4,880,086, entitled Adjustable Vibration Damper, which corresponds to Federal Republic of Germany Patent No. 37 19 113), the damping force of which can be adjusted. For this purpose, a damping valve equipped with an axially movable valve body and a valve seat controls the effective cross section of a damping passage. The electromagnetically activated damping valve comprises a number of individual parts, e.g. magnetic armatures, valve bodies and the armature guide surrounding the magnetic armature, where the individual parts have the normal manufacturing tolerances. For functional reasons, the armature of the electromagnet must coincide very precisely on its end surface with the barrel of the armature guide, and at the same time the valve cone or face must assume the sealed position. If manufacturing tolerances exist in the axial direction, the valve strokes will be different.
To prevent such tolerances or spreads, one of the inside parts can be manufactured with a certain amount of oversize and can be machined to the proper size after measurement. Such spreads can also be eliminated by installing prefabricated spacer discs, but for that method there must be a correspondingly graduated assortment of spacer discs available. The two methods described above, however, are unsuitable for the mass production of such electromagnetically activated damping valves.